Sub-namespaces are converted into underscores. The
Sensio\BlogBundle\Controller\UserProfileController::showDetails() action
will resolve to @SensioBlog/user_profile/show_details.html.twig

And if the only parameters to pass to the template are method arguments, you
can use the vars attribute instead of returning an array. This is very
useful in combination with the @ParamConverterannotation: